Illumination source for optical metrology

Abstract

The present disclosure relates to an illumination source for optical metrology. The source includes a matrix including 25 light emitting diodes (LEDs) arranged in 12 groups associated with 12 peak wavelength ranges. The peak wavelength range of the group is in the range of 400 to 1000 nanometers. Each group of LEDs is independently controlled, and each LED has a controllable intensity. The illumination source also includes a controller configured to selectively activate any combination of the LEDs and control the matrix based on a metrology method.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Provisional Patent Serial No. 63 / 496,946, filed on April 18, 2023, which is incorporated herein by reference. Technical Field

[0003] The present disclosure relates to the field of optical metrology, and in particular to an illumination source comprising a matrix of light emitting diodes (LEDs) arranged in different groups associated with different peak wavelength ranges. Background Art

[0004] Optical metrology is a key area that involves using light to measure various properties of an object. The field has a wide range of applications, from the inspection of semiconductor wafers to the analysis of biological samples.

[0005] Optical critical dimension (OCD) is a metrology technique used in the semiconductor industry to measure and characterize the size of features on semiconductor wafers. It plays a vital role in ensuring the quality and performance of integrated circuits.

[0006] OCD relies on the principle of optical scatterometry, which involves analyzing light scattered from a patterned wafer surface to extract information about its dimensions. By measuring the intensity and phase of the scattered light, OCD can determine critical dimensions such as line width, space, and height with high precision and accuracy.

[0007] A major advantage of OCD is its non-destructive nature, allowing in-line measurements to be made during the semiconductor manufacturing process without physical contact with the wafer. This enables real-time monitoring and control of critical dimensions, ensuring that manufactured devices meet required specifications.

[0008] OCD can provide valuable information about dimensional variations across the wafer and between different wafers in a batch. This data is critical for process optimization, yield improvement, and quality control. By detecting and quantifying deviations from expected dimensions, OCD helps identify process variations and potential problems early, allowing corrective action to be taken.

[0009] OCD is especially valuable in advanced semiconductor manufacturing processes where feature sizes become increasingly smaller and more challenging to measure using traditional techniques. As industry continues to push the limits of miniaturization, OCD provides a critical tool for ensuring the quality and performance of nanoscale devices.

[0010] A major component in an optical metrology system is the illumination source, which provides the light that interacts with the sample being measured.

[0011] QTH lamps, also known as quartz tungsten halogen lamps, are a type of incandescent lamp commonly used in a variety of applications, including photography, microscopy, and industrial lighting. These lamps are known for their high color temperature, excellent color rendering, and long life.

[0012] A key feature of the QTH lamp is the use of a tungsten filament enclosed in a quartz envelope. This design allows the lamp to operate at a higher temperature, producing a higher color temperature than a standard incandescent lamp. The quartz envelope also provides better thermal stability and resistance to chemical reactivity, making the QTH lamp suitable for use in harsh environments.

[0013] QTH lamps emit a continuous spectrum of light, which is important in applications that require accurate color reproduction, such as photography and microscopy. The high color rendering index (CRI) of QTH lamps ensures that colors appear natural and vivid, making them ideal for applications where color accuracy is critical.

[0014] Quartz tungsten halide (QTH) lamps provide a broad spectrum of light, making them suitable for a variety of applications. However, these sources have certain limitations. These QTH lamps are broadband light sources and need to be followed by bandpass filters for selectively filtering out unwanted wavelengths and limiting the emission to a narrower range. However, these filters have a fixed filtering function. Therefore, there is a need for an improved illumination source that can provide a versatile and customizable light output for optical metrology applications. Utility Model Content

[0015] According to an embodiment, an illumination source for optical metrology is provided. The illumination source includes a matrix including at least 25 light emitting diodes (LEDs) arranged in at least 12 different LED groups associated with at least 12 peak wavelength ranges. Wherein (i) the peak wavelength range of the first group and the second group is in the range of 400 to 500 nanometers, (ii) the peak wavelength range of the third group is in the range of 500 to 600 nanometers, (iii) the peak wavelength range of the fourth group is in the range of 600 to 700 nanometers, (iv) wherein the peak wavelength range of the fifth group, the sixth group and the seventh group is in the range of 700 to 800 nanometers, (v) the peak wavelength range of the eighth group and the ninth group is in the range of 800 to 900 nanometers, (vi) the peak wavelength range of the tenth group, the eleventh group and the twelfth group is in the range of 900 to 1000 nanometers.

[0016] According to an embodiment, the peak wavelength range of the first group is in the 400 to 405 nanometer sub-range, the peak wavelength range of the second group is in the 450 to 455 nanometer sub-range, the peak wavelength range of the third group is in the 525 to 530 nanometer sub-range, the peak wavelength range of the fourth group is in the 670 to 680 nanometer sub-range, the peak wavelength range of the fifth group is in the 700 to 705 nanometer sub-range, and the peak wavelength range of the sixth group is in the 725 to 750 nanometer sub-range.

[0017] According to an embodiment, the peak wavelength range of the seventh group is in the 785 to 790 nanometer sub-range, the peak wavelength range of the eighth group is in the 825 to 830 nanometer sub-range, the peak wavelength range of the ninth group is in the 860 to 870 nanometer sub-range, the peak wavelength range of the tenth group is in the 905 to 910 nanometer sub-range, the peak wavelength range of the eleventh group is in the 940 to 950 nanometer sub-range, and the peak wavelength range of the twelfth group is in the 985 to 990 nanometer sub-range.

[0018] According to an embodiment, each of the third to eleventh groups consists of more LEDs than the first to fourth groups, and the twelfth group has the highest number of LEDs of any of the groups.

[0019] According to an embodiment, each of the first to fourth groups consists of a single LED, each of the fifth to tenth groups consists of a pair of LEDs, the eleventh group consists of three LEDs, and the twelfth group consists of six LEDs.

[0020] According to an embodiment, each LED of any of the groups is controlled independently of any other LED of the matrix.

[0021] According to an embodiment, a group is controlled independently of any other group of the matrix.

[0022] According to an embodiment, each LED of the matrix has a controllable intensity.

[0023] According to an embodiment, a controller is also included.

[0024] According to an embodiment, the controller is configured to selectively activate any combination of any LEDs of the matrix.

[0025] According to an embodiment, the controller is configured to select from a first plurality of red lighting combinations, from a second plurality of infrared lighting combinations, and from a third plurality of blue lighting combinations.

[0026] According to an embodiment, the controller is configured to control at least one of the groups to illuminate the sample continuously.

[0027] According to an embodiment, the controller is configured to control at least one of the groups to illuminate the sample non-continuously.

[0028] According to an embodiment, the controller is configured to control the matrix based on a metrology method.

[0029] According to an embodiment, the controller is configured to control the matrix to illuminate the sample with different combinations of LEDs during different illumination pulses.

[0030] According to an embodiment, the matrix may include 25 or more LEDs, such as 6×6 LEDs, 7×7 LEDs, 8×8 LEDs, 6×5 LEDs, 5×7 LEDs, etc.

[0031] Depending on the embodiment, the LEDs are arranged in a rectangular array, a square array, or an array of any other shape.

[0032] According to an embodiment, the number of groups exceeds twelve.

[0033] According to an embodiment, the matrix may include 25 or more LEDs. For example, it may include 36 LEDs, 48 ​​LEDs, etc.

[0034] It has been found that the specific combination of wavelength ranges of the 12 sets of LEDs is well suited for metrology of a wide range of samples and structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 An example of a method is shown;

[0036] Figure 2 Examples of illumination sources are shown; and

[0037] Figure 3 Examples of images generated using different lighting schemes are shown. DETAILED DESCRIPTION

[0038] According to an embodiment, an illumination source for optical metrology is provided, the illumination source comprising a matrix comprising 25 light emitting diodes (LEDs) arranged in 12 different groups of LEDs associated with 12 peak wavelength ranges, wherein (i) the peak wavelength range of the first and second groups is in the range of 400 to 500 nanometers, (ii) the peak wavelength range of the third group is in the range of 500 to 600 nanometers, (iii) the peak wavelength range of the fourth group is in the range of 600 to 700 nanometers, (iv) the peak wavelength range of the fifth, sixth and seventh groups is in the range of 700 to 800 nanometers, (v) the peak wavelength range of the eighth and ninth groups is in the range of 800 to 900 nanometers, and (vi) the peak wavelength range of the tenth, eleventh and twelfth groups is in the range of 900 to 1000 nanometers.

[0039] According to an embodiment, the peak wavelength range of the first group is in the 400 to 405 nanometer sub-range, the peak wavelength range of the second group is in the 450 to 455 nanometer sub-range, the peak wavelength range of the third group is in the 525 to 530 nanometer sub-range, the peak wavelength range of the fourth group is in the 670 to 680 nanometer sub-range, the peak wavelength range of the fifth group is in the 700 to 705 nanometer sub-range, and the peak wavelength range of the sixth group is in the 725 to 750 nanometer sub-range.

[0040] According to an embodiment, the peak wavelength range of the seventh group is in the 785 to 790 nanometer sub-range, the peak wavelength range of the eighth group is in the 825 to 830 nanometer sub-range, the peak wavelength range of the ninth group is in the 860 to 870 nanometer sub-range, the peak wavelength range of the tenth group is in the 905 to 910 nanometer sub-range, the peak wavelength range of the eleventh group is in the 940 to 950 nanometer sub-range, and the peak wavelength range of the twelfth group is in the 985 to 990 nanometer sub-range.

[0041] According to an embodiment, each of the third to eleventh groups consists of more LEDs than the first to fourth groups, and the twelfth group has the highest number of LEDs of any of the groups.

[0042] According to an embodiment, each of the first to fourth groups consists of a single LED, each of the fifth to tenth groups consists of a pair of LEDs, the eleventh group consists of three LEDs, and the twelfth group consists of six LEDs.

[0043] According to an embodiment, each LED of any of the groups is controlled independently of any other LED of the matrix.

[0044] According to an embodiment, a group is controlled independently of any other group of the matrix.

[0045] According to an embodiment, each LED of the matrix has a controllable intensity.

[0046] According to an embodiment, the lighting source comprises a controller.

[0047] According to an embodiment, the controller is configured to selectively activate any combination of any LEDs of the matrix.

[0048] According to an embodiment, the controller is configured to select from a first plurality of red lighting combinations, from a second plurality of infrared lighting combinations, and from a third plurality of blue lighting combinations.

[0049] According to an embodiment, the controller is configured to control at least one of the groups to continuously illuminate the sample.

[0050] According to an embodiment, the controller is configured to control at least one of the groups to illuminate the sample non-continuously.

[0051] According to an embodiment, the controller is configured to control the matrix based on a metrology method.

[0052] According to an embodiment, the controller is configured to control the matrix to illuminate the sample with different combinations of LEDs during different illumination pulses.

[0053] An illumination source is provided that can replace currently used QTH lamps with filter wheels used in pattern recognition and autofocus (AF) modules of integrated metrology tools.

[0054] The illumination source is cost effective. Some costs were reduced by replacing the QTH lamps that operate continuously with LEDs that are off most of the time and activated during image acquisition, which lasts very short periods of time.

[0055] The lighting source is compact and can replace existing QTH lamp lighting modules.

[0056] The lighting source exhibits improved performance (compared to QTH lighting modules) based on the advantageous use of LEDs (eg—by increasing / amplifying wavelength / range—eg, IR, blue, power consumption, etc.) for pattern recognition (PR).

[0057] The illumination source may emit radiation of different colors—for example, red (IR) radiation as well as radiation of other colors.

[0058] The illumination source supports modes that match current and future challenges, allows for maximum flexibility in minimum time, increases reliability levels, has enough power to illuminate samples with only one color, and exhibits a large dynamic range that allows for a large number of illumination configurations.

[0059] The illumination source may use a matrix of LEDs capable of varying and / or mixing emission colors, with each LED or group of LEDs being independently controlled.

[0060] At least one LED of the matrix may be a multi-color LED.

[0061] The versatility of the illumination source allows supporting a wide range of metrology methods, an advantage in addressing pattern recognition challenges. The illumination source allows generating methods with more baseline combinations than is the case today, when methods should be generated for each layer.

[0062] During evaluation of a sample, the illumination can be changed rapidly, providing rich information about the sample.

[0063] Figure 1 An example of method 100 is shown.

[0064] According to an embodiment, method 100 comprises step 110 of configuring the lighting matrix by determining which LEDs of the matrix to operate during an evaluation iteration, when to operate any LED of the matrix and at what intensity. Step 110 may be performed at an LED resolution or a set of LED resolutions.

[0065] According to an embodiment, step 110 is followed by a step 120 of illuminating the sample during an evaluation iteration.

[0066] According to an embodiment, step 120 includes directing radiation from a matrix of 25 light emitting diodes (LEDs) onto the sample for measurement purposes. This matrix is ​​organized into twelve groups, each corresponding to a specified wavelength range. The purpose of this configuration is to provide a light source that can be adjusted to meet the specific requirements of the metrology task.

[0067] The matrix allows each LED to be controlled independently, enabling adjustment of intensity and wavelength combinations. The controller is responsible for activating any combination of LEDs and can be programmed to illuminate the sample in a continuous or non-continuous manner based on predetermined parameters, or to vary the illumination during different pulses.

[0068] The matrix is ​​designed to enable independent management of each LED, which allows fine-tuning of light output to achieve the desired lighting distribution. This feature is critical to obtaining accurate measurements in metrology, where the accuracy of characterization may depend on the specificity of the light source.

[0069] Steps 110 and 120 involve configuration and operation of a matrix designed for metrology, providing each LED with a customizable and precise illumination source capable of emitting light over a wide range of wavelengths at independently controllable intensities.

[0070] Step 120 involves the independent management of each LED within the structured arrangement. This step allows for adjustment of the intensity, on / off state, and illumination duration of each LED. The purpose of this capability is to tailor the light output to meet specific metrology task requirements. For example, if a specific feature on a sample requires illumination with a specific wavelength and intensity, only the LEDs corresponding to that wavelength range can be activated at the desired intensity level.

[0071] Method 100 involves the use of a matrix and a controller, and software executed by the controller for the illumination process. The controller executes instructions that specify which LEDs should be activated, their intensity levels, and their illumination timing. This enables the illumination source to produce various combinations of wavelength ranges and intensities, which is necessary for high-quality measurements where different materials and structures may require different illumination conditions.

[0072] The parameters set in step 110 include electrical characteristics related to the operation of each LED, such as voltage and current, which are adjusted to determine the intensity of the emitted light. The controller is configured to modify these parameters for each LED without affecting other LEDs. In addition, the timing control is precise to ensure that the LEDs are activated and deactivated at predetermined moments, especially in situations where the lighting is not continuous.

[0073] Thus, step 120 involves the independent adjustment of each LED (or each group) in the matrix to provide the specific illumination for metrology. This step is necessary to achieve the flexibility and control required to accurately measure a variety of samples under different conditions.

[0074] Step 110 may benefit from having one or more groups including more than a single LED, with the number of LEDs in each group affecting the intensity and coverage of the light that can be emitted, with higher counts allowing for greater illumination capabilities within their respective wavelength ranges.

[0075] The intensity of each LED (or each group of LEDs) can be adjusted individually, allowing precise control of the lighting pattern. This capability enables the light output to be adjusted to meet the specifications of different metrology processes, which may require a specific intensity and wavelength combination for optimal measurement accuracy.

[0076] In practice, these steps are accomplished through the engineering and production of the LED matrix, the programming of the controller that manages the intensity and activation of each LED, and the incorporation of the illumination source into an optical metrology system. The ability of the controller to selectively activate and modulate the LEDs enables the system to be adapted to a variety of measurement scenarios, providing a flexible and effective tool for the characterization of samples.

[0077] Figure 2 is an example of an illumination source 200 that can be used as a component in optical metrology to enable precise sample illumination with customizable wavelength ranges and intensities. LED matrix 202 is part of illumination source 200 and consists of 25 LEDs organized into 12 LED groups, each corresponding to a specific wavelength range. This arrangement allows for independent control and intensity adjustment of each LED, helping to tailor illumination for metrology applications.

[0078] An LED matrix 202 serves as the core of the illumination source 200, with its 25 light emitting diodes grouped into 12 LED groups. Each group is associated with a peak wavelength range identified by a wavelength range, enabling the selection of specific wavelengths for different metrology tasks. The ability to independently operate each LED (or at least each group independently) allows for customized illumination patterns, which is necessary to achieve the desired contrast and resolution on the surface of the sample for accurate measurements. The intensity of each LED is adjustable, providing control over the lighting conditions.

[0079] The system controller 204 communicates with the illumination source 200 to manage the activation and modulation of the LEDs. It can activate any combination of LEDs, allowing for a range of lighting scenarios. The controller can execute continuous or pulsed illumination sequences based on the measurement strategy. It also follows predefined metrology methods, ensuring repeatability and consistency of measurements. The controller's ability to select from a variety of lighting combinations, including red, infrared, and blue light, enables the system to adapt to different metrology challenges. By controlling the matrix according to these methods, the system can illuminate the sample with optimal lighting conditions during each measurement cycle, improving the reliability and accuracy of the metrology process.

[0080] The LED matrix 202 serves as the core of the illumination source for optical metrology. It consists of 25 light emitting diodes arranged in 12 groups, each group corresponding to a specific peak wavelength range. The first and second groups emit in the 400 to 500 nanometer range, while subsequent groups cover a wavelength range of up to 1000 nanometers, extending from the visible spectrum to the infrared.

[0081] Each LED in the matrix can be controlled independently, allowing individual LEDs or groups of LEDs to be selected for activation. This feature enables customization of the illumination pattern to match the requirements of the metrology task, whether it requires continuous or pulsed light, a single wavelength or a combination. The intensity of each LED is adjustable, providing a means of fine-tuning the illumination power for the sample being inspected.

[0082] The system controller 204 interfaces with the LED matrix and executes the metrology method. It selects the appropriate combination of LEDs and controls their operation, whether continuous operation for steady-state measurements or pulsed operation for time-resolved analysis. This adaptability is key to adjusting the metrology system to a variety of samples and measurement conditions, ensuring accurate data acquisition.

[0083] The system controller 204 is the component of the optical metrology illumination source that enables precise control of the LED matrix 202. It manages the individual LED groups and their wavelength ranges to achieve the specific illumination conditions required for sample analysis.

[0084] The system controller (204) is responsible for the operation of the LED matrix 202, which includes the ability to independently manage the intensity of each LED. This functionality allows customization of the illumination profile, enabling the selection of specific wavelengths for targeted sample analysis. The controller is able to activate any combination of LEDs within the matrix, which is essential when different metrology methods are required. This feature allows rapid switching between LED combinations without significantly affecting throughput.

[0085] According to an embodiment, some LEDs meet at least one of the following requirements:

[0086] 1. Rise to full strength within 100μs.

[0087] 2. After the shutdown operation, reduce to 10% of their full strength -5 .

[0088] Table 1 shows an example of properties of 12 groups of LEDs.

[0089]

[0090] Table 1

[0091] Depending on the implementation, the matrix is ​​manipulated in any one or more of the following ways:

[0092] a. Operation of one or more groups of LEDs.

[0093] b. Operation of one or more LEDs of one or more groups of LEDs.

[0094] c. Continuous operation of one or more LEDs.

[0095] d. Non-continuous operation of one or more LEDs.

[0096] e. Continuous operation of one or more groups of LEDs.

[0097] f. Non-continuous operation of one or more groups of LEDs.

[0098] In addition, the controller is configured to support both continuous and non-continuous illumination modes, providing flexibility in the time domain of sample exposure. It can also execute complex illumination strategies, such as changing the LED combination during different illumination pulses, which is critical to optimizing the image quality captured during the metrology process and ensuring reliable feature detection.

[0099] System controller 204 acts as a command center for LED matrix 202, dictating the operating modes and intensity levels of the LEDs. This enables illumination source 200 to provide customized illumination conditions for precise optical measurements.

[0100] According to an embodiment, the LED matrix 202 is optically coupled to optical coupling and uniformity optics 206 , such as an adapter that includes a uniformizer and ends with a fiber coupler interface 208 that interfaces with an optical fiber or fiber bundle 210 .

[0101] Examples of fiber bundles are fiber bundles 945-00760-00 or 945-01468. Both have an effective diameter of 4 mm. Other diameters may be provided.

[0102] The lighting configuration may change within an evaluation iteration or during testing of the matrix.

[0103] A test sequence may include:

[0104] 1.800ms continuous operation of IR LED.

[0105] 2. 11-second pulse operation of either the red group and / or infrared group.

[0106] - Pulse duration 4-30 ms

[0107] - Continuous pulses with at least 10ms off time between pulses.

[0108] - Up to 4 such pulse groups separated by an off time of at least 200ms.

[0109] -8 seconds off time between the sequence described in 1, 2 and the next sequence.

[0110] Table 1 shows examples of different lighting configurations for 12 groups of LEDs:

[0111] Figure 3 Examples of images of a sample, generally referred to as 300 , obtained under different lighting conditions are shown.

[0112] In the detailed description, many specific details are set forth to provide a thorough understanding of the present application. However, it will be appreciated by those skilled in the art that the present application can be practiced without these specific details. In other examples, well-known methods, processes, and components are not described in detail to avoid confusing the present application.

[0113] The subject matter which is regarded as the present application is particularly pointed out and distinctly claimed in the concluding portions of the specification. However, the organization and method of operation of the application, as well as the objects, features, and advantages thereof, may be best understood by reference to the detailed description when read in conjunction with the accompanying drawings.

[0114] It should be understood that for simplicity and clarity of illustration, the elements shown in the figures are not necessarily drawn to scale. For example, for clarity, the size of some elements may be exaggerated relative to other elements. In addition, where deemed appropriate, reference numerals may be repeated in the drawings to indicate corresponding or similar elements.

[0115] Since the embodiments shown in the present application can in most cases be implemented using electronic components and circuits known to those skilled in the art, in order to understand and appreciate the basic concepts of the present application and in order not to confuse or distract from the teachings of the present application, the details will not be explained to a greater extent than is considered necessary as shown above.

[0116] Any reference in the specification to a method should be applied mutatis mutandis to a system capable of performing the method.

[0117] Any reference in the specification to a system should apply mutatis mutandis to a method that may be performed by the system.

[0118] Any values ​​(eg, time values, dimensions, signal values, frequencies, standards) are merely non-limiting examples.

[0119] In the foregoing specification, the application has been described with reference to specific examples of embodiments of the application. It will, however, be evident that various modifications and changes may be made therein without departing from the broader spirit and scope of the application as set forth in the appended claims.

[0120] Furthermore, the terms "front", "rear", "top", "bottom", "upper", "lower", etc., if any, in the specification and claims are used for descriptive purposes and not necessarily for describing permanent relative positions. It should be understood that the terms so used are interchangeable under appropriate circumstances, such that the embodiments of the application described herein are, for example, capable of operation in other orientations than those shown or otherwise described herein.

[0121] As discussed herein, connection can be suitable for, for example, transmitting signals from corresponding nodes, units or devices via intermediate devices or to corresponding nodes, units or devices. Any type of connection of transmitting signals. Therefore, unless otherwise implied or indicated, connection can be, for example, direct connection or indirect connection. Connection can be illustrated or described with reference to a single connection, multiple connections, unidirectional connection or bidirectional connection. However, different embodiments can change the implementation of connection. For example, a separated unidirectional connection can be used instead of a bidirectional connection, and vice versa. In addition, multiple connections can be replaced by a single connection that transmits multiple signals in serial or time multiplexing mode. Similarly, a single connection that carries multiple signals can be separated into various connections that carry a subset of these signals. Therefore, there are many options for transmitting signals.

[0122] Although a specific conductivity type or polarity of the potential has been described in the examples, it should be understood that the conductivity type and polarity of the potential can be reversed.

[0123] Each signal described herein can be designed as either positive logic or negative logic. In the case of a negative logic signal, the signal is active low, where the logically true state corresponds to a logic level zero. In the case of a positive logic signal, the signal is active high, where the logically true state corresponds to a logic level one. Note that any signal described herein can be designed as either a negative or positive logic signal. Therefore, in alternative embodiments, those signals described as positive logic signals can be implemented as negative logic signals, and those signals described as negative logic signals can be implemented as positive logic signals.

[0124] Furthermore, the terms "assertion" or "setting" and "negation" (or "de-assertion" or "clearing") are used herein when referring to a signal, status bit, or the like assuming its logically true or logically false state, respectively. If the logically true state is a logic level one, the logically false state is a logic level zero. If the logically true state is a logic level zero, the logically false state is a logic level one.

[0125] Those skilled in the art will recognize that the boundaries between logic blocks are merely illustrative, and that alternative implementations may merge logic blocks or circuit elements, or impose an alternative decomposition of functionality onto various logic blocks or circuit elements. It should be understood, therefore, that the architectures depicted herein are merely exemplary, and that in fact many other architectures may be implemented that implement the same functionality.

[0126] Any arrangement of components that achieve the same functionality is effectively "associated" so as to achieve the desired functionality. Thus, any two components combined herein to achieve a particular functionality may be considered "associated" with each other so as to achieve the desired functionality, without regard to architectures or intermediate components. Likewise, any two components so associated may also be considered "operably connected" or "operably coupled" to each other so as to achieve the desired functionality.

[0127] Furthermore, those skilled in the art will recognize that the boundaries between the above operations are merely illustrative. Multiple operations may be combined into a single operation, a single operation may be distributed among additional operations, and operations may be performed at least partially overlapping in time. Furthermore, alternative implementations may include multiple instances of a particular operation, and the order of the operations may be changed in various other implementations.

[0128] Also for example, in one embodiment, the examples shown may be implemented as circuits located on a single integrated circuit or within the same device. Alternatively, the examples may be implemented as any number of separate integrated circuits or separate devices interconnected with each other in a suitable manner.

[0129] However, other modifications, changes and substitutions are possible. Accordingly, the specification and drawings are to be regarded as illustrative rather than restrictive.

[0130] In the claims, any reference numerals placed between brackets shall not be construed as limiting the claim. The word "comprising" does not exclude the presence of other elements or steps than those listed in the claim. In addition, the terms "one" or "an" as used herein are defined as one or more. In addition, the use of introductory phrases such as "at least one" and "one or more" in the claims shall not be construed as implying that the introduction of another claim element by the indefinite article "one" or "an" shall limit any particular claim containing such introduced claim element to an application containing only one such element, even when the same claim includes the introductory phrases "one or more" or "at least one" and indefinite articles such as "one" or "an". The same is true for the use of definite articles. Unless otherwise stated, terms such as "first" and "second" are used to arbitrarily distinguish the elements described by these terms. Therefore, these terms are not necessarily intended to indicate the time or other priority of these elements. The fact that certain measures are recorded in mutually different claims does not mean that the combination of these measures cannot be used advantageously.

[0131] Although certain features of the present application have been illustrated and described herein, many modifications, substitutions, changes and equivalents will now occur to those skilled in the art. Therefore, it should be understood that the appended claims are intended to cover all such modifications and changes that fall within the true spirit of the present application.

Claims

1. An illumination source for optical metrology, characterized in that: The illumination source comprises: a matrix comprising 25 light emitting diodes (LEDs), the LEDs being arranged in 12 different groups of LEDs associated with 12 peak wavelength ranges, wherein (i) the peak wavelength range of the first and second groups is within the range of 400 to 500 nanometers, (ii) the peak wavelength range of the third group is within the range of 500 to 600 nanometers, (iii) the peak wavelength range of the fourth group is within the range of 600 to 700 nanometers, (iv) the peak wavelength range of the fifth, sixth and seventh groups is within the range of 700 to 800 nanometers, (v) the peak wavelength range of the eighth and ninth groups is within the range of 800 to 900 nanometers, and (vi) the peak wavelength range of the tenth, eleventh and twelfth groups is within the range of 900 to 1000 nanometers.

2. The illumination source according to claim 1, characterized in that The peak wavelength range of the first group is in the 400 to 405 nanometer sub-range, the peak wavelength range of the second group is in the 450 to 455 nanometer sub-range, the peak wavelength range of the third group is in the 525 to 530 nanometer sub-range, the peak wavelength range of the fourth group is in the 670 to 680 nanometer sub-range, the peak wavelength range of the fifth group is in the 700 to 705 nanometer sub-range, and the peak wavelength range of the sixth group is in the 725 to 750 nanometer sub-range.

3. The illumination source according to claim 1, characterized in that The peak wavelength range of the seventh group is in the 785 to 790 nanometer sub-range, the peak wavelength range of the eighth group is in the 825 to 830 nanometer sub-range, the peak wavelength range of the ninth group is in the 860 to 870 nanometer sub-range, the peak wavelength range of the tenth group is in the 905 to 910 nanometer sub-range, the peak wavelength range of the eleventh group is in the 940 to 950 nanometer sub-range, and the peak wavelength range of the twelfth group is in the 985 to 990 nanometer sub-range.

4. The illumination source according to claim 1, characterized in that Each of the third to eleventh groups consists of more LEDs than the first to fourth groups, and the twelfth group has the highest number of LEDs of any of the groups.

5. The illumination source according to claim 1, characterized in that Each of the first to fourth groups consists of a single LED, each of the fifth to tenth groups consists of a pair of LEDs, the eleventh group consists of three LEDs, and the twelfth group consists of six LEDs.

6. The illumination source according to claim 1, characterized in that Each LED of any of the groups is controlled independently of any other LED of the matrix.

7. The illumination source according to claim 1, characterized in that The group is controlled independently of any other group of the matrix.

8. The illumination source according to claim 1, characterized in that Each LED of the matrix has a controllable intensity.

9. The illumination source according to claim 1, characterized in that A controller is also included.

10. The illumination source according to claim 9, characterized in that The controller is configured to selectively activate any combination of any LEDs of the matrix.

11. The illumination source according to claim 9, characterized in that The controller is configured to select from a first plurality of red illumination combinations, from a second plurality of infrared illumination combinations, and from a third plurality of blue illumination combinations.

12. The illumination source according to claim 9, characterized in that The controller is configured to control at least one of the groups to continuously illuminate the sample.

13. The illumination source according to claim 9, characterized in that The controller is configured to control at least one of the groups to illuminate the sample non-continuously.

14. The illumination source according to claim 9, characterized in that The controller is configured to control the matrix based on a metering method.

15. The illumination source according to claim 9, characterized in that The controller is configured to control the matrix to illuminate the sample with different combinations of LEDs during different illumination pulses.

16. The illumination source according to claim 1, characterized in that The matrix comprises more than 25 LEDs.

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